A federal appeals court says immigration detainees who were held at a private prison in Colorado can move forward with a lawsuit alleging they were required to do manual labor for as little as $1 a day while awaiting possible deportation.

The GEO Group, which operates the 1,500-bed facility in Aurora, argued the case should not have been certified as a class action on behalf of 62,000 people who had been held in the center over the past decade.

The 10th U.S. Circuit Court of Appeals ruled Friday the detainees could proceed with claims the center violated the federal Trafficking Victims Protection Act.

GEO has said its work program is voluntary and complies with Immigration and Customs Enforcement guidelines. Boulder attorney Brandt Milstein said detainees were forced to work under the threat of solitary confinement.